In the first decade of their existence Athletic selected English players for the team,[13][3][5][14] but since 1912[15][16] they have adhered to a policy of allowing only players born in the Basque Country or who learned their football skills at a Basque club to play for them.[1][4][17][18][5][19][14][7] The motto used to describe the reasoning behind it is "Con cantera y afición, no hace falta importación" (English: "with home-grown talent and local support, you don't need foreigners").[20]

Back in 1911, a dispute occurred between Real Sociedad and Athletic Bilbao regarding the latter fielding ineligible English players in the 1911 Copa del Rey;[3][14] they had also employed the services of several (non-Basque) players from Atlético Madrid which was then a branch of the Bilbao club.[32][33] This led to the Royal Spanish Football Federation introducing a rule for the next year's competition that all players must be Spanish citizens.[5][16] As a large proportion of the players in that early era were Basque,[24][19] relying on locals was no impediment to Athletic and they chose to maintain that approach even when the regulations were relaxed some years later.

The policy has been praised as a symbol of localised football being successful at the highest level,[4][34][16] as well as preserving a strong regional identity[9][35][6] and being a way for Basque nationalism to be moderately expressed.[9][8][35][36][24] It has been described as discriminatory for only allowing Basque players to play for Athletic Bilbao,[4][37][17][7] although it has been suggested that the policy is working for them since Athletic are one of only three clubs (along with Real Madrid and Barcelona) never to have been relegated from La Liga.[9][20][21][6][19][14]

Due to a relatively low immigrant population in the region,[4][38][37] the policy also had the consequence of Athletic Bilbao being the last club in La Liga to have never fielded a black player. That was ended in 2011 when Jonás Ramalho, whose father is Angolan, made his debut.[4][3][23] In 2015 Iñaki Williams (born in Bilbao to Ghanaian immigrant parents)[39][40] became Athletic's first black goalscorer.[34][41] Prior to Ramalho, in 2000 the first African-born player in the club's youth system was Blanchard Moussayou[42] whose promising career was curtailed by injury; some years later, he stated his belief that it was 'twice as hard' for a black player to make an impact at the club.[43]Gorka Luariz, a forward of mixed ethnicity capped by Equatorial Guinea in 2018, spent time in Athletic's youth system despite being born in Zaragoza as his upbringing was almost entirely in the Basque region.[44]

Former academy trainee Yuri Berchiche, who rejoined Athletic in the summer of 2018 as one of the club's most expensive signings,[45][6] has an Algerian father but showed no interest in playing for their national team when the matter was put to him.[46][47]

As of 2019, Athletic's academy teams include a small number of players of an ethnic minority (mostly Afro-Spaniard) background, including Cameroon-born goalkeeper Chris Atangana,[48] forward Nico Williams (the younger brother of Iñaki),[49] and defender Loic Boum, also of Cameroonian origin, who having been orphaned as a child was a ward of the Government of Navarre when he moved to the club in 2014.[50][51]

Laporte's signing in 2009 prompted debate regarding the definitions of the policy, as he had no link to the Basque region through birth or residency, and a blood link only via great-grandparents.[53][54][55][18] He did join a team in the territory, Aviron Bayonnais,[56][55] but only by arrangement after the initial approach from Athletic, as he was too young to move to a club outside France at the time – he arrived formally in 2010.[34]

Antoine Griezmann, the French forward developed by Real Sociedad, was the subject of debate regarding his eligibility for a theoretical move to Athletic as he emerged as an elite player in 2012.[58] Hailing from Burgundy, he arrived at the San Sebastián club aged 14[59] but only to play football for their academy teams rather than for some other non-sporting reason, and has no connection to the French Basque Country other than attending school there after signing for Real.

The opinions of some (including Athletic's academy director José María Amorrortu) [58] were that his training at a Basque club from a young age adhered to the policy,[60] while others insisted that he had the same (ineligible) status as any adult player transferred in by Real and the other local professional clubs.[61]

In any event, Griezmann showed little interest in joining Athletic,[59] subsequently moved on to Atlético Madrid[58] and was voted the world's third best player in 2016,[62] making any move to Bilbao unlikely in the medium term. In respect of any future players of a similar trajectory, Athletic's position on recruitment remains unconfirmed.

In 2011, media sources claimed that Athletic had shown interest in young Mexican midfielder Jonathan Espericueta[64] but no such move materialised, and the player himself (who did later play in Spain with Villarreal B) stated that his Basque connection was as distant as a great-great-grandfather.[65]

Conversely, players born in the Basque Country but raised elsewhere are considered eligible.[23] In the years prior to the Spanish Civil War, Athletic undertook a project named 'Operation Return', seeking players born in the Basque region who had emigrated to other countries. One of the few who actually made a competitive appearance for the club was Nemesio Tamayo who had begun his career in his adopted homeland of Chile and also played in Mexico before a brief spell in his birthplace.[85] The arrival of Bilbao-born Emilio Aldecoa in 1947 was unusual as he had spent the past decade of his life in England, having been evacuated as a teenage refugee of the Civil War.[86][87][88] Another member of that refugee group was the club's star goalkeeper of the era Raimundo Pérez Lezama, although he had returned home much sooner on the outbreak of World War II; a third Basque refugee Sabino Barinaga turned down an offer from Athletic and joined Real Madrid.[89]

It was once the case that Athletic would usually recruit from the Biscay province surrounding Bilbao[23] while the other leading clubs Real Sociedad and Osasuna would focus on players from their respective provinces Gipuzkoa and Navarre. In recent decades (with the pool of potential players declining due to a low birth rate in the area),[84] Athletic expanded their recruitment in these other areas in their efforts to accommodate the best players with any Basque links. This saw many talented players from San Sebastián[98] and Pamplona[99] join the club, and also caused Real Sociedad to abandon their own Basque policy in the face of the competition for signings.[100][18]

That change of focus also led to fewer players from the home province being selected; in a 2011 fixture, none of the Athletic starters or used substitutes were from Biscay.[12][112][113] However, in subsequent years more local players made the grade, and the situation appears unlikely to occur again in the near future – twelve of the 25 players in the 2016–17 squad were born in Biscay, and in November 2017 a study showed that 77% of players in the academy teams hailed from the province.[114]

On the other hand, the definitions of the philosophy are stretched occasionally to accommodate promising youngsters with little Basque connection, which does not always sit well with some of the club's followers.

Enric Saborit, originally from Catalonia, who graduated through the youth and reserve levels to reach the first team, caused questions to be asked when he signed in 2008; he had no connection with the region by birth or blood, but while already 16 years old and playing in RCD Espanyol's cantera teams, he moved to Vitoria-Gasteiz where his mother had relocated for work two years earlier. As soon as he became a resident of the territory, Saborit was deemed eligible by Athletic to play for the club.[115][37][116]

In summer 2017, Athletic recruited Youssouf Diarra, an 18-year-old forward born in Mali who was raised in Catalonia and had spent the past two years playing for clubs in Navarre after moving these to continue his education, which the club deemed sufficient under the policy,[117][118] but apparently decided the circumstances by which Ibrahima Deng, a teenage migrant from Senegal via Tenerife, came to play for Basque club SD Amorebieta did not fit the policy[119] (Deng later joined another local professional club, SD Eibar).[120] The previous year, Athletic had signed 16-year-old Colombia-born defender Deiby Ochoa, who lived in La Rioja and had only ever played for clubs in that region.[121][122] Like Diarra, he had attended trial matches at the Lezama training centre.

However, despite having invited Ochoa (the spelling of whose name was changed to the Basque Otxoa in club records) to join,[123] in October 2017 it was announced that Athletic's youth training camp in Oion – a village in Álava, but just a few miles from Logroño – would no longer accept players who did not fit the Athletic philosophy, effectively excluding around 150 Riojan youngsters of various ages from the system and leaving only around ten Basques across the squads.[124][125][90] Past recruits born in that region, who were considered eligible due to their formative club being Osasuna or Real Sociedad, include José Mari García, Santiago Ezquerro, David López and Borja Viguera;[7] however, the justifications for allowing Luis de la Fuente and later Daniel Aranzubia to join Athletic's youth system directly from Riojan clubs were less clear.[90]

In January 2018, Athletic announced a new signing who was more obviously non-Basque by ethnicity: 25-year-old Cristian Ganea, a Romanian international[126] who was also born in that country and had only played for Romanian clubs for the past five years. But prior to that, he had spent his teenage years living in Basauri just outside Bilbao and had featured for local teams (including Basconia, Athletic's farm team at semi-professional level who have a separate amateur and juvenile structure), meaning he too was eligible under the 'learned skills at a Basque club' aspect of the policy.[127][128] A year later, the Bosnian international forward Kenan Kodro joined the club, but his Basque credentials beyond his name (born and raised in San Sebastián and a Real Sociedad youth product) were very robust.[129]